1. Field of the Invention
The present invention relates to a projector, and more particularly, it relates to a projector including a laser beam emitting portion.
2. Description of the Background Art
A projector or the like including a laser beam emitting portion is known in general, as disclosed in each of Japanese Patent Laying-Open Nos. 2004-279943, 2002-341285, 2002-296677 and 2001-30537, for example.
The aforementioned Japanese Patent Laying-Open No. 2004-279943 discloses an image display including laser beam output means constituted of a plurality of laser beam emitting portions outputting laser beams and a control portion reducing power consumption by stopping the laser output of a partial laser beam emitting portion included in the plurality of laser beam emitting portions thereby lowering brightness of light.
The aforementioned Japanese Patent Laying-Open No. 2002-341285 discloses an optical scanner including a laser diode generating an optical beam, a movable mirror for scanning an object with the optical beam emitted from the laser diode, an electrode driving portion for driving the movable mirror, a synchronous sensor detecting the optical beam and outputting a synchronous detection signal and a terminal sensor detecting the optical beam on a scanning terminal. The optical scanner disclosed in the aforementioned Japanese Patent Laying-Open No. 2002-341285 is formed to time the scanning with the optical beam on the basis of the synchronous detection signal. Further, the optical scanner disclosed in the aforementioned Japanese Patent Laying-Open No. 2002-341285 is formed to determine that the movable mirror does not correctly scan the object with the optical beam and to stop supplying current to the laser diode when no detection signals are obtained from the synchronous sensor and the terminal sensor even if a voltage applied to the electrode driving portion exceeds a prescribed value in a state where the laser diode is turned on.
The aforementioned Japanese Patent Laying-Open No. 2002-296677 discloses an optical scanning type projector including a laser source emitting three laser beams, i.e., red, green and blue laser beams, an optical modulator modulating the laser beams, a horizontal optical chopper for partially blocking the laser beams modulated in the optical modulator, a polygonal mirror horizontally scanning a screen with the laser beams received from the horizontal optical chopper and a galvanomirror displaying an image on the screen by vertically scanning the screen with the laser beams employed for horizontally scanning the screen through the polygonal mirror. The optical scanning type projector disclosed in the aforementioned Japanese Patent Laying-Open No. 2002-296677 is formed to highlight boundaries between pixels in the image displayed on the screen by blocking the laser beams to separate adjacent pixels from each other in the horizontal optical chopper.
The aforementioned Japanese Patent Laying-Open No. 2001-30537 discloses an optical scanner including a semiconductor laser emitting a laser beam, a rotary polyhedral mirror for scanning an object with the laser beam emitted from the semiconductor laser and an optical detector detecting pass timing of the laser beam scanning the object. The optical scanner disclosed in the aforementioned Japanese Patent Laying-Open No. 2001-30537 is so formed, when there is deviation between the pass timing of the laser beam detected by the optical detector and image information, as to correct the deviation by deleting or adding data of the image information on the position where the deviation is present. This optical scanner is formed to emit the laser beam or to stop emitting the laser beam on the basis of the image information by varying optical output of the semiconductor laser beam.
However, the image display described in the aforementioned Japanese Patent Laying-Open No. 2004-279943 stops the laser output from the partial laser beam emitting portion included in the plurality of laser beam emitting portions while the remaining laser beam emitting portions continuously output the laser beams, and hence the temperature is disadvantageously easily increased in the remaining laser beam emitting portions continuously outputting the laser beams. Therefore, luminous efficiency (optical output with respect to current) is disadvantageously reduced in the laser beam emitting portions continuously outputting the laser beams, due to the increase in the temperature.
The optical scanner described in the aforementioned Japanese Patent Laying-Open No. 2002-341285 stops supplying current to the laser diode in an abnormal state of determining that the movable mirror does not correctly scan the object with the optical beam, and does not stop supplying the current to the laser diode in a normal state of determining that the movable mirror correctly scans the object with the optical beam. Therefore, it is conceivable that the laser diode regularly continuously emits the optical beam while the normal state continues. In this case, however, the temperature is disadvantageously easily increased in the laser diode. Therefore, luminous efficiency of the laser diode is disadvantageously reduced due to the increase in the temperature.
The optical scanning type projector described in the aforementioned Japanese Patent Laying-Open No. 2002-296677 blocks the laser beams to separate adjacent pixels from each other in the horizontal optical chopper, while the laser source emits the laser beams continuously, and hence the temperature is disadvantageously easily increased in the laser source. Therefore, luminous efficiency is disadvantageously reduced in the laser source, due to the increase in the temperature.
The optical scanner described in the aforementioned Japanese Patent Laying-Open No. 2001-30537 may conceivably stop emission of the laser beam on the basis of the image information, while the semiconductor laser may continuously emit the laser beam depending on the image information. In this case, the temperature is disadvantageously easily increased in the semiconductor laser. Therefore, luminous efficiency of the semiconductor laser is disadvantageously reduced due to the increase in the temperature.